Photosensitive/photothermic composition and process

ABSTRACT

A COMBINATION OF A MERCURY HALIDE WITH THIOUREA DIOXIDE IN PHOTOSENSITIVE AND THERMOSENSITIVE ELEMENTS AND COMPOSITIONS PROVIDES REDUCED PRINT-OUT. A LATENT IMAGE IN THESE ELEMENTS OR COMPOSITIONS CAN BE DEVELOPED BY HEATING THE ELEMENT OR COMPOSITION. THE PHOTOSENSITIVE AND THERMOSENSITIVE ELEMENT CAN CONTAIND PHOTOSENSITIVE SILVER HALIDE AND ADDENDA COMMONLY EMPLOYED IN PHOTOSENSITIVE AND THERMOSENSITIVE MATERIALS, SUCH AS ACIVATOR-TONING AGENTS, SENSITIZING DYES AND REDUCING AGENTS.

United States Patent O 3,692,526 PHOTOSENSITIVE/PHOTOTHERMIC COMPOSI- TION AND PROCESS Cynthia Geer Uliiing, Fairport, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y.

No Drawing. Filed Apr. 1, 1971, Ser. No. 130,434 Int. Cl. G03c 1/28, 5/24 US. Cl. 96108 12 Claims ABSTRACT OF THE DISCLOSURE A combination of a mercury halide with thiourea dioxide in photosensitive and thermosensitive elements and compositions provides reduced print-out. A latent image in these elements or compositions can be developed by heating the element or composition. The photosensitive and thermosensitive element can contain photosensitive silver halide and addenda commonly employed in photosensitive and thermosensitive materials, such as activator-toning agents, sensitizing dyes and reducing agents.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to photosensitive elements, compositions and processes containing a combination of certain compounds to provide reduced print-out upon processing. In one of its aspects, it relates to a photosensitive element containing a combination of photosensitive silver halide with a mercury salt and thiourea dioxide. In another of its respects, it relates to a photosensitive and thermosensitive element suitable for developing a latent image with heat containing the described combination of mercury salt with thiourea dioxide. A further aspect relates to a photosensitive composition containing photosensitive silver halide and the described combination of mercury salt and thiourea dioxide. Another aspect relates to a process of developing a latent image in a photosensitive and a thermosensitive element containing a photosensitive silver halide, a mercury salt and thiourea dioxide by heating the element.

DESCRIPTION OF THE STATE OF THE ART It is well known to develop a latent image in a photo- .graphic silver halide element using so-called dry processing with heat. After exposure, the resulting latent image in the photographic. element is developed and, in some cases, stabilized merely by heating the photographic element. Such a process is described, for example, in US. Pats. 3,301,678 of Humphlett et 211. issued Ian. 31, 1967, 3,152,904 of Sorensen et al. issued Oct. 13, 1964, 3,392,020 of Yutzy et a1. issued July 9, 1968, and 3,457,075 of Morgan et al. issued July 22, 1969, and Belgian Pat. 705,872. Mercury compounds have also been employed in materials for processing with heat as described, for example, in U.S. Pats. 1,939,232 of Sheppard et al. issued Dec. 12, 1933, 2,681,277 of Morrison issued June 15, 1954, 1,976,302 of Sheppard et a1. issued Oct. 9, 1934, 2,095,839 of Sheppard et a1. issued Oct. 12, 1937, and'Belgian Pats. 729,043 and 729,042. None of these references suggests compounds which can be employed in combination with mercury salts to provide reduced printout in photosensitive materials, especially photosensitive materials for processing with heat.

Mercury compounds have been employed for various purposes in photographic materials as described, for example, in US. Pats. 2,728,664 of Carroll et al. issued Dec. 22, 1955, 2,728,663 of Allen et a1. issued Dec. 22, 1955, 2,723,914 of Suchow issued Nov. 15, 1955, 2,324,060 of Boughton issued July 13, 1943, and 2,874,047 of Van der Meulen et al. issued Feb. 17, 1959. None of these references, however, relates to combinations of materials that can be employed with mercury compounds to provide reduced print-out upon processing.

Thiourea dioxide, also known as formamidine sulfinic acid, has been employed in chemical sensitization of photographic emulsions as described in US. Pat. 2,983,609 of Allen et al. issued May 9, 1961, and for fogging photographic silver halide emulsions as described in US. Pat. 3,062,651 of Hillson issued Nov. 6, 1962. It was surprisingly found that when thiourea dioxide is used alone in photosensitive materials for processing with heat, no image is found, as demonstrated in the following comparative Example 3. No suggestion is made in the art that any reduction in print-out can be provided by a combination of thiourea dioxide with a mercury salt.

There has been a continuing need to provide photosensitive and thermosensitive elements, compositions and processes which provide increased image density with reduced print-out in background'areas.

SUMMARY OF THE INVENTION It has been found according to the invention that a combination of a mercury salt, such as a mercury halide, with thiourea dioxide in a photosensitive element, composition and/or process provides surprisingly reduced background print-out. These photosensitive materials are suitable for processing with heat.

As indicated in the following comparative Examples 2 and 3, surprisingly, when the mercury salt, e.g., mercuric chloride, or thiourea dioxide is used alone in the absence of the combination, no satisfactory image is produced.

DETAILED DESCRIPTION OF THE INVENTION Mercury halides which are suitable according to the invention are those which, in combination with thiourea dioxide, provide reduced print-out upon processing a photosensitive element as described. Mercury halides which can be used for this purpose are, for example, mercuric chloride, mercurous chloride, mercuric bromide, mercurous bromide, mercuric iodide and/0r mercurous iodide.

A suitable concentration of mercury halide and thiourea dioxide and suitable ratio of mercury halide to thiourea dioxide can vary depending, for instance, on the processing conditions, particular photosensitive component, particular reducing agent and the like. A test to determine a suitable concentration is set out in Example 1. Usually a ratio of 0.10 mg. to mg. of mercury halide to .01 mg. to 100 mg. of thiourea dioxide is suitable.

One embodiment of the invention is a photosensitive element comprising a support, photosensitive silver halide, mercury halide, as described, and thiourea dioxide. A preferred embodiment, however, is a photosensitive and thermosensitive element comprising a support,

(a) Photosensitive silver halide,

(b) An oxidation-reduction image-forming combination comprising (i) a heavy metal salt oxidizing agent, with (ii) a reducing agent,

(c) Mercury halide, and

(d) Thiourea dioxide.

Another embodiment of the invention is accordingly a photosensitive composition comprising photosensitive silver halide, mercury halide and thiourea dioxide. This composition can be, for example, a photosensitive and thermosensitive composition comprising:

(a) Photosensitive silver halide,

(b) An oxidation-reduction image-forming combination, as described,

(0) Mercury halide, and

(d) Thiourea dioxide.

An especially suitable photosensitive and thermosensitive element or composition comprises the described combination of mercury halide with thiourea dioxide with:

(a) A polyvinyl butyral binder,

(b) Photosensitive silver halide,

An oxidation-reduction image-forming combination comprising:

(i) silver behenate with (ii) a reducing agent comprising 2,2'-dihydroxy-l,lbinaphthyl and/ or 2,2 methylene-bis-(6 tbutyl-4- methylphenol), and

(d) An activator-toning agent comprising phthalimide and/or phthalazinone with, optionally, a zinc acetate image amplifier, l-phenethyl-Z-picolinium bromide or trimethyl phenylammonium bromide, a stabilizer precursor such as 5-acetyl-4-methyl-2-(3-oxobutylthio)thiazole, and a blue-speed-increasing sensitizing dye such as 3-carboxy methyl 5- I: 3-methyl'-2( 3H)-thiazolinylidene isopropylideneJrhodanine, 3 ethyl 5 [(3-ethyl-2(3H)-benzothiazolylidene)isopropylidene] Z-thio-2,4-oxazolidenedione or l-carboxymethyl 5 [(3-ethyl-2(3H)-benzoxazolylidene)ethylidene]-3-phenyl-2-thiohydantoin.

After exposure of the described photosensitive and thermosensitive element, the resulting latent image is developed merely by heating the element. Accordingly, another embodiment of the invention is a method of developing a latent image in a photosensitive and thermosensitive element comprising a support,

(a) Photosensitive silver halide,

(b) An oxidation-reduction image-forming combination comprising (i) a heavy metal salt oxidizing agent, as described,

with (ii) a reducing agent, also 'as described,

(0) Mercury halide and (d) Thiourea dioxide, comprising heating said element to about 80 C. to about 250 C. A temperature range of about 100 C. to about 180 C. is usually suitable for developing a desired image. By increasing or decreasing the length of time of heating, a higher or lower temperature within the described range can be employed. A developed image is typically produced within a few seconds, such as about 0.5 to about 60 seconds.

Processing is usually carried out under ambient conditions. Temperatures, pressures and humidity outside normal atmospheric conditions can be employed if desired. However, normal atmospheric conditions are preferred.

Any suitable means can be used for providing the desired processing temperature range. The heating means can be a simple hot plate, iron, roller or the like.

In some cases, if desired, an element can be prepared wherein the described silver halide or one or more of the other components of the described compositions can be in one layer and other components in other layers. For example, an element according to the invention can comprise a support, a layer containing photographic silver halide and a separate layer comprising other components of the described composition.

The described element or composition contains photosensitive silver halide. In a photosensitive and thermosensitive composition, it is believed the photosensitive silver halide acts as a catalyst for the oxidation-reduction image-forming combination. A typical concentration range of photosensitive silver halide is from about 0.005 to about 0.50 mole of photosensitive silver halide per mole of heavy metal salt oxidizing agent. Examples of suitable photosensitive silver halides are silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide, or mixtures thereof. The photosensitive silver halide can be coarseor fine-grain, very fine-grain silver halide being especially useful. The emulsion containing the photosensitive silver halide can be prepared by any of the well-known procedures in the photographic art, such as single-jet emulsions, double-jet emulsions, such as Lippman emulsions, ammoniacal emulsions, thiocyanate or thioether ripened emulsions, such as those described in U.S. Pats. 2,222,264 of Nietz et 'al. issued Nov. 14, 1940, 3,320,069 of Illingsworth issued May 15, 1967, and 3,271,157 of McBride issued Sept. 6, 1966. Surfaceimage silver halide emulsions can be used. If desired, mixtures of surfaceand internal-image silver halide emulsions can be used as described in U.S. Pat. 2,996,332 of Luckey et al. issued Apr. 15, 1961. Negative-type emulsions can be used. The silver halide can be a regular-grain silver halide such as described in Klein and Moisar, Journal of Photographic Science, vol. 12, No. 5, Septemher-October 1964, pages 24225 1.

The silver halide employed in the practice of the invention can be unwashed or washed to remove soluble salts. In the latter case, the soluble salts can be removed by chill-setting and leaching or an emulsion containing the silver halide can be coagulation-washed.

The silver halide employed in the practice of the invention can be sensitized with chemical sensitizers, such as with reducing agents; sulfur, selenium or tellurium c0mpounds; gold, platinum or palladium compounds; or combinations of these. Suitable procedures are described, for example, in U.S. Pats. 1,623,499 of Shepard issued Apr. 5, 1927, 2,399,083 of Waller et al. issued Apr. 23, 1946, 3,297,447 of McVeigh issued Jan. 10, 1967, and 3,297,- 446 of Dunn issued Jan. 10, 1967.

Photosensitive silver halide employed in the practice of the invention can be protected against the production of fog and can be stabilized against loss of sensitivity during keeping. Suitable antifoggants and stabilizers, e.g., used alone or in combination include, for example, thiazolium salts; azaindenes; mercury salts as described, for example, in U.S. Pat. 2,728,663 of Allen et al. issued Dec. 27, 1955; urazoles; sulfocatechols; oximes described, for example, in British Pat. 623,448; nitron; nitroindazoles; polyvalent metal salts described, for example, in U.S. Pat. 2,839,405 of Jones issued June 17, 1958; platinum, palladium and gold salts described, for example in U.S. Pats. 2,566,263 of Trivelli et a1. issued Aug. 28, 1951, and 2,597,915 of Yutzy et al. issued May 27, 1952.

Reducing agents, which are typically silver halide developing agents, can be used in the described photosensitive compositions and elements. These are typically employed as the reducing agent in the described oxidationreduction imageforming combination. Suitable silver halide developing agents include, for example, polyhydroxybenzenes such as hydroquinone developing agents, e.g., hydroquinone, alkyl-substituted hydroquinones as exemplified by tertiary butylhydroquinone, methylhydroquinone, 2,5-dimethylhydroquin0ne and 2,6-dimethylhydroquinone; catechols and pyrogallol; halo-substituted hydroquinones such as chlorohydroquinone or dichlorohydroquinone; alkoxy-substituted hydroquinones such as methoxyhydroquinone or ethoxyhydroquinone; methylhydroxynaphthalene; phenylenediamine developing agents; methylgallate; arninophenol developing agents, such as 2,4-diaminophenols and methylaminophenols; ascorbic acid developing agents such as ascorbic acid, ascorbic acid ketols and ascorbic acid derivatives such as those described in U.S. Pat. 3,337,342 of Green issued Aug. 22, 1967; hydroxylamine developing agents such as N,N-di- (Z-ethoxyethyl)hydroxylamine; 3-pyrazolidoue developing agents such as l-phenyl-3-pyrazolidone and 4-methy1- 4-hydroxymethyl-1-phenyl-3-pyrazolidone including those described in British Pat. 930,572 published July 3, 1963; hydroxytetronic acid, hydroxytetronamide developing agents, and reductone developing agents such as anhydro piperidino hexose reductone.

Suitable organic reducing agents which can be employed in the described oxidation-reduction image-forming combination are typically phenolic reducing agents such as substituted phenols and naphthols. These include,

in addition to those described, 2,2-methylene-bis-phenols, such as 2,2'-rnethylene-bis-(6-t-butyl-4-methylphenol), and bis naphthols such as bis-fi-naphthols of the formula:

wherein R and/or R are hydrogen, alkyl with 1 to 3 carbon atoms, alkoxy, e.g., alkoxy containing 1 to 2 carbon atoms, such as methoxy or ethoxy; halogen, nitro, amino or a diazonium halide salt and n is or 1. Suitable bis- 8- naphthols which can be employed in the practice of the invention include:

2,2'-dihydroxy-l l'-binaphthyl, 6,6'-dibromo-2,2-dihydroxy-1,1-binaphthyl, 6,6'-dinitro-2,2-dihydroxy-l,1-binapthyl, and/ or bis- (Z-hydroxyl-naphthyl) methane.

The described reducing agents are suitable in a range of concentration; however, they are especially suitable at a concentration from about 0.10 to about 0.75 mole of reducing agent per mole of oxidizing agent, e.g., per mole of silver behenate.

The described photosensitive and thermosensitive compositions and elements comprise a heavy metal oxidizing agent, such as a heavy metal salt of an organic acid. The heavy metal salts of the organic acids should be resistant to darkening under illumination to prevent undesired deterioration of a developed image. An especially suitable class of heavy metal salts of organic acids is represented by the water-insoluble silver salts of long-chain fatty acids which are stable to light. Compounds which are suitable silver salts include silver behenate, silver stearate, silver oelate, silver laurate, silver hydroxystearate, silver caprate, silver myristate and silver palmitate.

Other suitable carboxylic acid silver salt oxidizing agents, which are not silver salts of long-chain fatty acids, include silver benzoate, silver 4'-n-octadecyloxydiphenyl- 4-carboxylate, silver-o-aminobenzoate, silver acetamidobenzoate, silver furoate, silver camphorate, silver-p-phenylbenzoate, silver phenylacetate, silver salicylate, silver butyrate, silver terephthalate, silver phthalate, silver acetate and silver acid phthalate.

Oxidizing agents which are not silver salts of a carboxylic acid can be employed, if desired, such as silver phthalazinone, silver benzotriazole and silver saccharin. Oxidizing agents which are not silver salts can be employed, if desired, such as zinc oxide, gold stearate, mercuric behenate, auric behenate and the like, but silver salts are preferred.

It is desirable to employ an activator-toning agent in the elements, compositions and processes of the invention to obtain a desired image, particularly when phenolic reducing agents are used.

One class of suitable activator-toning agent is a hetero cyclic activator-toning agent containing at least one nitrogen atom and of the formula:

Where R is hydrogen, hydroxyl, or a metal ion such as potassium, sodium, lithium, silver, gold or mercury; Z represents atoms completing a heterocyclic nucleus, especially a 5- or G-member heterocyclic nucleus. The atoms completing the heterocyclic nucleus can be, for example,

or an alkylene group containing 3 to 4 carbon atoms. The atoms completing the heterocyclic nucleus can contain various substituent groups, such as amino, alkyl amino, e.g., methylamino or ethylamino, hydroxyl, carbamyl and the like. A suitable activator-toning agent within this class is a cyclic imide of the formula:

(III) 'M wherein R is hydrogen, hydroxyl, or a metal ion such as potassium, sodium, lithium, silver, gold or mercury; Z repersents carbon atoms of a series completing a cyclic imide nucleus, typically consisting of from 5 to 6 carbon atoms, e.g., a phthalimide or succinimide nucleus. The atoms of the cyclic imide nucleus can contain various substituent groups, especially amino, alkyl, such as alkyl containing l to 5 carbon atoms, such as methyl, ethyl, propyl, butyl, or pentyl or aryl, such as aryl containing 6 to 20 carbon atoms, such as phenyl, tolyl and xylyl. Suitable activator-toning agents of structure HI are:

phthalimide, N-hydroxyphthalimide, N-potassium phthalimide, N-silver phthalimide, N-mercury phthalimide, succinimide and/ or N-hydroxysuccinimide.

Other so-called activator-toning agents can be employed in combination with or in place of the described cyclic imide activator-toning agents. Typically, a heterocyclic organic toning agent containing at least 2 hetero atoms in the heterocyclic ring of which at least 1 is a nitrogen atom is employed. These are described, for example, in U.S. Pat. 3,080,254 of Grant issued Mar. 5, 1963. Suitable toners include, for example, phthalazinone, phthalic anhydride, Z-acetylphthalazinone and 2-phthalylphthalazinone.

The described activator-toning agents are suitable in a range of concentration; however, they are especialy suitable at a concentration of about 0.10 mole to about 1.5 moles of activator-toning agent per mole of described oxidizing agent, e. g., per mole of silver behenate.

A nonaqueous, polar, organic solvent such as a compound containing a moiety, in a described photosensitive and thermosensitive element or composition suitable for processing with heat can in many cases provide improved maximum image densities. Suitable nonaqueous solvents include, for example, tetrahydrothiophene-1,1-dioxide, 4-hydroxybutanoic acid lactone and methylsulfinylmethane.

A divalent metal salt which has the property of amplifying the developed image can be employed in the practice of the invention to cause an increase in maximum image density. A suitable divalent metal salt image amplifier is zinc acetate, cadmium acetate or cupric acetate. The described image-amplifying compounds are suitable in a range of concentration of about 0.005 to about 0.20 mole of divalent metal salt image amplifier per mole of heavy metal salt oxidizing agent.

It is desirable in some cases to employ an image stabilizer precursor in the described elements or compositions of the invention. These can be employed in the practice of the invention to reduce further the amount suitable in a range of concentration; however, they are especially suitable at a concentration from about 0.002 mole to about 0.10 mole of stabilizer precursor per mole of heavy metal salt oxidizing agent, e.g., per mole of silver behenate in an element or composition as described.

A range of colorless onium halides can be employed in the described elements or compositions to provide an additional increase in photosensitivity, i.e., speed, and in some cases to obtain a reduction in background density. A suitable speed-increasing onium halide compound is a quaternary ammonium halide, quaternary phosphonium halide and/or a tertiary sulfonium halide, e.g., l-phenethyl-Z-picolinium bromide, tetraethylphosphonium bromide or trimethylsulfonium iodide. An optimum concentration can be determined for each onium halide. An onium halide is added at various concentrations to a final coating dispersion as described. An especially suitable onium halide is trimethylphenylammonium bromide which is typically employed at a concentration of about 0.010 mole to about 0.05 mole per mole of photosensitive silver halide.

An element and compositions described and used in the practice of the invention can contain various colloids alone or in combination as vehicles, binding agents and in various layers. Suitable materials are typically bydrophobic, but hydrophilic materials can also be employed. They are transparent or translucent and include both naturally occurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as water-soluble polyvinyl compounds like poly(vinyl pyrrolidone), acrylamide polymers and the like. Other synthetic polymeric compounds which can be employed include dispersed vinyl compounds such as a latex form and particularly those which increase dimensional stability of photographic materials. Suitable synthetic polymers include those described in U.S. Pats. 3,142,586 of Nottorf issued July 28, 1964, 3,193,386 of White issued July 6, 1955, 3,062,674 of Houck et al. issued Nov. 6, 1962, 3,220,844 of Houck et al. issued Nov. 30, 1965, 3,287,289 of Ream et al. issued Nov. 22, 1966, and 3,411,911 of Dykstra issued Nov. 19, 1968. Effective polymers include water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates, and those which have crosslinking sites which facilitate hardening or curing, as well as those having recurring sulfobetaine units as described in Canadian Pat. 774,054. Preferred high-molecularweight materials and resins include polyvinyl butyral, cellulose acetate butyrate, polymethyl methacrylate, poly- (vinyl pyrrolidone), ethyl cellulose, polystyrene, polyvinyl chloride, chlorinated rubber, polyisobutylene, butadiene-styrene copolymers, vinyl chloride-vinyl acetate copolymers, copolymers of vinyl acetate, vinyl chloride and maleic acid and polyvinyl alcohol.

The photosensitive and other materials employed in the practice of the invention and described herein can be coated on a wide variety of supports. Typical supports include cellulose nitrate film, cellulose ester film, poly- (vinylacetal) film, polystyrene film, poly(ethylene terephthalate) film, polycarbonate film and related films or resious materials, as Well as glass, paper, metal and the like. Typically, a flexible support is employed, especially a paper support which can be partially acetylated or coated with baryta and/ or an alpha-olefin polymer, particularly a polymer of an alpha-olefin containing 2 to carbon atoms such as polyethylene, polypropylene, ethylenebutene copolymers and the like.

The photosensitive and other hardenable layers of an element used in the practice of this invention can be hardened by various organic or inorganic hardeners, alone or in combination, such as aldehydes, and blocked aldehydes, ketones, carboxylic and carbonic acid derivatives, sulfonate esters, sulfonyl halides and vinyl sulfonyl ethers, halogen compounds, epoxy compounds, aziridines, active olefins, isocyanates, carbodiimides, mixed-function hardeners and polymeric hardeners such as oxidized polysaccharides like dialdehyde starch and oxyguargum and the like.

The photosensitive elements used in the practice of the invention can contain antistatic or conducting layers. Such layers can comprise soluble salts such as chlorides, nitrates and the like, evaporated metal layers, ionic polymers such as those described in U.S. Pats. 2,861,056 of Minsk issued Nov. 18, 1958, and 3,206,312 of Sterman et al. issued Sept. 14, 1965, or insoluble inorganic salts such as those described in U.S. Pat. 3,428,451 of Trevoy issued Feb. 18, 1969. The photosensitive and thermosensitive elements can also contain antihalation materials and antihalation dyes.

The photosensitive layers or other layers employed in the practice of the invention can contain plasticizers and lubricants. Suitable plasticizers and lubricants include, for example, polyalcohols such as glycerin and diols described, for example, in U.S. Pat. 2,960,404 of Milton et al. issued Nov. 1, 1966; fatty acids or esters such as those described in U.S. Pat. 3,121,060 of Robijns issued Mar. 11, 1952; U.S. Pat. 3,121,060 of Duane issued Feb. 11, 1964; and silicone resins such as those described in British Pat. 955,061.

The photosensitive layers or other layers employed in the practice of the invention can contain surfactants such as saponin; anionic compounds such as alkyl aryl sulfonates described, for example, in U.S. Pat. 2,600,831 of Baldsiefen issued June 17, 1962; amphoteric compounds such as those described in U.S. Pat. 3,133,816 of Ben- Ezra issued May 19, 1964; and adducts of glycidol and an alkyl phenol such as those described in British Pat. 1,022,878.

If described, the photosensitive elements employed in the practice of the invention can contain matting agents such as starch, titanium, dioxide, zinc oxide, silica, polymeric beads including beads described, for example, in U.S. Pats. 2,922,101 of Jelley et al. issued July 11, 1961, and 2,761,245 of Lynn issued Feb. 1, 1955.

The photosensitive elements and compositions employed in the practice of the invention can contain brightening agents including stilbenes, triazines, oxazoles and coumarin brightening agents. Water-soluble brightening agents can be used such as those described in German Pat. 972,067 and U.S. Pat. 2,933,390 of McFall et al. issued Apr. 19, 1960, or dispersions of brighteners can be used such as those described in German Pat. 1,150,- 274, U.S. Pat. 3,406,070 of Oetiker et al. issued Oct. 15, 1968, and French Pat. 1,530,244.

The various layers including the photosensitive and thermosensitive layers of an element employed in the practice of the invention can contain light-absorbing materials, filter dyes, antihalation dyes and absorbing dyes such as those described in U.S. Pats. 3,253,921 of Sawdey issued May 31, 1966, 2,274,782 of Gasper issued Mar. 3, 1942, 2,527,583 of Silberstein et al. issued Oct. 31, 1950, and 2,956,879 of Van Campen issued Oct. 18, 1960. If desired, the dyes can be mordanted, for example, as described in U.S. Pat. 3,282,699 of Jones et 211. issued Nov. 1, 1966.

The photosensitive and thermosensitive layers used in the practice of the invention can be coated by various coating procedures including dip coating, air-knife coating, curtain coating or extrusion coating using hoppers such as described in U.S. Pat. 2,681,294 of Beguin issued June 15, 1954. If desired, two or more layers can be coated simultaneously such as by the procedures described in U.S. Pat. 2,761,791 of Russell issued Sept. 4, 1956, and British Pat. 837,095.

If desired, the photosensitive silver halide can be prepared in situ in the photosensitive and thermosensitive coatings of an element employed in the practice of the invention. Such a method is described, for example, in

U.S. Pat. 3,457,075 of Morgan et al. issued July 22, 1969. For example, a dilute solution of a halogen acid such as hydrochloric acid, can be applied to the surface of a thin coating containing an organic silver salts, such as silver behenate, on a suitable substrate followed by removal of the solvent if desired. Silver halide is thus formed in situ throughout the surface of the coating of the organic silver salt.

The photosensitive silver halide can be prepared on the oxidizing agent, such as silver behenate or silver stearate, or other organic silver salt, prior to application of the silver halide on the support employed. This is also described in U.S. Pat. 3,457,075 of Morgan et al. issued July 22, 1969; for example, a halogen acid such as hydrochloric acid or hydrobromic acid can be mixed with an organic silver salt in a suitable reaction medium. A halide salt more soluble than the organic silver salt can be added to a suspension of the organic silver salt to form the silver halide. A suitable reaction medium includes water or other solutions which do not interfere with the reaction.

Stability to print-out from light exposure is further increased by employing highly purified materials; for example, freedom from halides and sulfides increases stability to light exposure. The use of highly purified silver behenate can, for example, reduce propensity to print-out in background areas of an element prepared according to the invention.

Spectral-sensitizing dyes can be used conveniently to confer additional sensitivity to the elements and compositions of the invention. For instance, additional spectral sensitization can be obtained by treating the silver halide with a solution of a sensitizing dye in an organic solvent or the dye can be added in the form of a dispersion as described in British Pat. 1,154,781. For optimum results, the dye can either be added to the emulsion as a final step or at some earlier stage.

Sensitizing dyes useful in sensitizing silver halide emulsions are described, for example, in U.S. Pats. 2,526,632 of Brooker et al. issued Oct. 24, 1950, 2,503,776 of Sprague issued Apr. 11, 1950, 2,493,748 of Brooker et al. issued Jan. 10, 1950, and 3,384,486 of Taber et a1. issued May 21, 1968. Spectral sensitizers, which can be used, include the cyanines, merocyanines, complex (trinuclear or tetranuclear) cyanines, holopolar cyanines, styryls, hemicyanines such as enamine, hemicyanines, oxonols and hemioxonols. Dyes of the cyanine classes can contain such basic nuclei as the thiazolines, oxazolines, pyrrolines, pyridines, oxazoles, thiazoles, senelazoles and imidazoles. Such nuclei can contain alkyl, alkylene, hydroxyalkyl, sulfoalkyl, carboxyalkyl, aminoalkyl, and enamine groups that can be fused to carbocyclic or heterocyclic ring systems either unsubstituted or substituted with halogen, phenyl, alkyl, haloalkyl, cyano, or alkoxy groups. The dyes can be symmetrical or unsymmetrical and can contain alkyl, phenyl, enamine or heterocyclic substituents on the methine or polymethine chain.

The mercocyanine dyes can contain the basic nuclei described, as well as acid nuclei such as thiohydantoins, rhodanines, oxazolidenediones, thiazolidenediones, barbituric acids, thiazolineones and malononitrile. These acid nuclei can be substituted with alkyl, alkylene, phenyl, carboxyalkyl, sulfoalkyl, hydroxyalkyl, alkoxyalkyl, alkylamine groups or heterocyclic nuclei. Combinations of these dyes can be used, if desired. In addition, supersensitizing addenda which do not absorb visible light may be included such as, for instance, ascorbic acid derivatives, azaindenes, cadmium salts and organic sulfonic acid as described in U.S. Pats. 2,933,390 of McFall et al. issued Apr. 19, 1960, and 2,937,089 of Jones et al. issued May 17, 1960.

The sensitizing dyes and other addenda used in the prac tice of the invention can be added from Water solutions or suitable organic solvent solutions can be used. The compounds can be added using various procedures including, for example, those described in U.S. Pats. 2,912,343 of 10 Collins et al. issued Nov. 10, 1959, 3,342,605 of McCrossen et al. issued Sept. 19, 1967, 2,996,287 of Audran is sued Aug. 15, 1961, and 3,425,835 of Johnson et al. issued Feb. 4, 1969.

Other addenda known to be useful in photosensitive and thermosensitive elements of this type, such as described in U.S. Pats. 3,152,904 of Sorensen and Shepard issued Oct. 13, 1964, and 3,457,075 of Morgan and Shely issued July 22, 1969, and British Pat. 1,161,777 published Aug. 20, 1969, can be employed in the practice of the invention.

The following examples are included for a further understanding of the invention.

EXAMPLE 1 This illustrates the invention.

A photosensitive silver halide-silver behenate dispersion is prepared by ball-milling the following components together for about 48 hours:

Silver behenate g 7.0 Behenic acid g 7.8 Polyvinyl butyral g 2.5 Sodium bromide 0.4

Acetone-toluene (1 to 1 parts by volume) ml 150.0

With the following components are mixed 2.0 ml. of the resulting silver halide-silver behenate dispersion:

2,2'-methylene-bis-(6-t-butyl-4-methylphenol) 5% by Weight in acetone) 2.0 l(2H)-phthalazinone (1.0% by weight in acetone) 2.0 Acetone-toluene (1 to 1 parts by volume) 1.5 Mercuric chloride (4.4 mg./ml. acetone) 0.5 Thiourea dioxide (1.0 mg./ml. acetone) 0.5

The resulting composition is coated on a suitable photographic paper support at a Wet thickness of 0.004 inch. Samples of the resulting photosensitive element are exposed for 20 seconds with tungsten light in a contact printer. The exposed photosensitive element is heated by contacting the side opposite the photosensitive coating with a curved hot metal block for 15 seconds while the metal block is at a temperature of C. The resulting developed image has a maximum reflection density of 1.00 and a minimum reflection density in the background areas of 0.24.

As a control, the above procedure is repeated with the exception that mercuric chloride and thiourea dioxide are omitted from the photosensitive material. The resulting developed image provides a maximum reflection density of 1.15 and a minimum reflection density in the background areas of 0.52. This indicates that the combination of mercuric chloride and thiourea dioxide provides significant reduction in background reflection density due to reduced print-out.

EXAMPLE 2 This is a comparative example.

The procedure set out in Example 1 is repeated with the exception that thiourea dioxide is omitted from the photosensitive material.

The resulting developed image provides no significant maximum reflection density and a minimum reflection density of 0.16.

EXAMPLE 3 This is a comparative example.

The procedure set out in Example 1 is repeated with the exception that mercuric chloride is omitted from the described photosensitive material.

Upon heating the exposed photosensitive element, high fog and no image are produced. The resulting photosensitive material contains an over-all density of 1.30.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention.

What is claimed is:

1. A photosensitive element comprising a support, photosensitive silver halide, mercury halide and thiourea dioxide.

2. A photosensitive element as in claim 1 wherein said mercury halide is mercuric chloride.

3. A photosensitive and thermosensitive element comprising a support,

(a) photosensitive silver halide,

(b) an oxidation-reduction image-forming combination comprising (i) a heavy metal salt oxidizing agent, with (ii) a reducing agent,

(c) mercury halide and (d) thiourea dioxide.

4. A photosensitive and thermosensitive element as in claim 3 wherein said mercury halide is mercuric chloride.

5. A photosensitive and thermosensitive element as in claim 3 comprising a support,

(a) photosensitive silver halide,

(b) an oxidation-reduction image-forming combination comprising (i) silver behenate with (ii) a phenolic reducing agent,

(c) phthalazinone,

(d) mercuric chloride and (e) thiourea dioxide.

6. A photosensitive composition comprising photosensitive silver halide, mercury halide and thiourea dioxide.

7. A photosensitive composition as in claim 6 comprising photosensitive silver halide, mercuric chloride and thiourea dioxide.

8. A photosensitive and thermosensitive composition comprising:

(a) photosensitive silver halide,

(b) an oxidation-reduction image-forming combination comprising (i) a heavy metal salt oxidizing agent, with (ii) a reducing agent,

(c) mercury halide and (d) thiourea dioxide.

9. A photosensitive and thermosensitive composition as in claim 8 comprising:

(a) photosensitive silver halide,

(b) an oxidation-reduction image-forming combination comprising 12 (i) silver behenate with (ii) a phenolic reducing agent,

(c) phthalazinone,

(d) mercuric chloride and (e) thiourea dioxide.

10. A method of developing a latent image in a photosensitive and thermosensitive element comprising a support,

(a) photosensitive silver halide,

(b) an oxidation-reduction image-forming combination comprising (i) a heavy metal salt oxidizing agent, with (ii) a reducing agent, (c) mercury halide and (d) thiourea dioxide, comprising heating said element to about 80 C. to about 250 C.

11. A method as in claim 10 of developing a latent image in a photosensitive and thermosensitive element comprising a support,

(a) photosensitive silver halide,

(b) an oxidation-reduction image-forming combination comprising (i) silver behenate with (ii) a phenolic reducing agent, (c) mercuric chloride and (d) thiourea dioxide, comprising heating said element to about 80 C. to about 250 C.

12. A method as in claim 11 wherein said element is heated to about 80 C. to about 250 C. for about 0.5 to about seconds.

References Cited UNITED STATES PATENTS 3,062,651 11/1962 Hillson 96l0l 3,457,075 7/1969 Morgan et al. 96-4 14.1 3,547,648 12/1970 Sagawa 961l4.l 3,531,286 9/1970 Renfrew 96l14.l 3,597,205 8/1971 Flannagan 96-64 NORMAN G. TORCHIN, Primary Examiner R. E. FICHTER, Assistant Examiner U.S. Cl. X.R.

96-48 HD, 114.1; 250 F 

